Building security systems have been in use for many years. Some of these systems allow for remote monitoring of, and provide for access control to, restricted areas. Access control is the ability to permit or deny the use of a particular credential by a particular entity. A security access control system determines who, where and when one is allowed to enter or exit an area. Electronic access control uses computers to solve the limitations of mechanical locks and keys. The electronic access control system grants access based on the credential presented. When access is granted, a door, for example, is unlocked for a predetermined time and the transaction is recorded in a database. When access is refused, the door remains locked and the attempted access is recorded. The system also monitors the door and alarms if the door is forced open or held open too long after being unlocked. A user can access a door with the use of a swipe/proximity access card, key fob, or the use of a biometric reader. There are many card technologies including magnetic stripe, bar code, proximity, Wiegand, RS-232, RS-485, contact smart cards, and contactless smart cards. Typical biometric technologies include fingerprint, facial recognition, iris recognition, retinal scan, voice, and hand geometry.
When a credential is presented to a reader, the reader sends the credential's information, typically an identifying numbered sequence, to a control panel which is a highly reliable processor. The control panel compares the credential's number to an access control list and other conditions, and either grants or denies the presented request, and sends a transaction log to the host computer database. When access is denied based on the access control list the door remains locked. If there is a match between the credential and the access control list, the control panel operates a relay that, in turn, unlocks the door. The control panel also ignores the subsequent door open signal to prevent an alarm. Often the reader provides feedback, such as a flashing red LED for an access denied and a flashing green LED for an access granted.
An access control point can be a door, turnstile, parking gate, elevator, or other physical barrier where granting access can be electrically or electro-mechanically controlled. Typically, the access point is a door. A typical electronically secured access control door deploys, at a minimum: 1) an electrified lock; 2) an access card reader; 3) a door status monitor; and 4) a request to exit device.
To maintain a building's security and to prevent tampering, all access control controllers (processors) must be installed within a secured space. Additionally, a typical security system will monitor the integrity of wiring between the alarm controller and the associated Remote Monitored Device (RMD). RMDs can be items such as, but not limited to, panic buttons, door status monitors, temperature monitors, alarm points and other low voltage inputs.
In order to prevent individuals from defeating various security measures, such as a door open alarm caused by an unauthorized door entry, various measures have been put into place to prevent defeating of the RMD. For cable fault and device status, a resistor is placed at the “end of line” (EOL), which is as close to the remote sensor/device as possible. The controller then transmits a low current through each resistor(s) configuration and depending on the amount of voltage read across the resistor(s) configuration, the controller then senses 1) the presence of the EOL resistor(s) and 2) the voltage value, which is dependent on the EOL value. By using this technique, with the use of, for example, two EOL resistors in a series/parallel arrangement, five separate conditions can be achieved: 1) Normal (secure); 2) Alarm; 3) Open; 4) Short; and 5) Trouble (measured voltage is out of expected range).
These EOL resistors are typically installed by hand as close to the device in the field as feasible and coupled to the controller. A problem past systems faced is that, when retrofitting a new security system, the new system could only be used with specific resistance values. This meant that the value of the EOL resistor(s) had to be known in advance and had to match the controller's designed and expected resistance values. For example, if the controller expects to sense a 1,000 ohm resistor, then the installer must install a resistor(s) of such value adjacent to the monitored device. If the installed resistor is for example 2,000 ohms, which would be out of the expected range of the controller, then the controller would issue a “trouble” notice. In order to return to normal, the installer then had to physically go to the EOL 2,000 ohm resistor(s), including first finding it and then replacing it with the correct value the controller was expecting.
Various systems have been proposed to help deal with this problem with varying degrees of success. For example, U.S. Pat. No. 7,256,683 (the '683 patent) and U.S. Patent Application Publication No. 2008/0007415 (the '415 appln.) both disclose a PLC controller for a security system that may be manually programmed to operate with various EOL resistors. For example, the '683 patent states that if the “system being replaced uses field resistors having a different value, then the EOL modules can be reprogrammed for that value.” (Col. 8, Ins. 1-3; see also, the '415 appln. p. 2, ¶12). However, a problem with the systems taught in these references is that when the new security system is installed, a technician is required to measure the resistance of each and every EOL resistance value in the various states of operation (e.g. resistance measurement for door open/closed, etc.) and then manually input this information into the system. While this is better than having to replace all the EOL resistors, this is still a very time-consuming and expensive process. Additionally, this process is inherently subject to human error in the measurement and inputting process.
Another problem with current security systems is that when a device goes into alarm, for example a card reader may be in alarm, there is no means of remotely determining the origin of the problem for trouble-shooting purposes. For example, a card reader may go into alarm for various reasons. Typically, a technician would be dispatched to the building, would access the security panel, and would then begin looking through the various devices to determine the origin of the alarm. Once located, the technician would then proceed to the location of the device and attempt to clear and/or fix the cause of the alarm. Often, the alarm can be cleared simply by resetting the device (e.g., disconnecting and reconnecting to power). Even though it was a relatively simple matter to clear the alarm, the technician had to spend significant time to travel to the building location, locate and identify the source of the alarm and then reset the device. This results in significant costs to the building owner.
Still another problem with current security systems is the size of the systems. For example, it is not uncommon for a security system that monitors and actuates thirty two doors to essentially cover an eight foot tall by eight foot wide space of a wall in an equipment room. Currently, systems are not only very large, but are also unsightly and are labor intensive to install.